The social dynamics of diffusion can be a powerful force in determining the timing and pace of fertility change, yet their role is not recognized in most conventional theories of fertility transition. This project will expand the conventional approach to fertility by examining systematically the causal contribution of social interaction. The research will be guided by new theoretical and empirical models of diffusion, and specifically by the organizing concepts of social learning and social influence, which together comprise what the investigators term social effects. The hypotheses derived from these organizing concepts will be tested using micro-level longitudinal data to be collected in two settings in southern and northern Ghana. Ghana provides an excellent setting for this research because its fertility transition is just getting underway. Here it is possible, via prospective data collection, to observe the social dynamics underlying the process of adoption of modern contraception from the earliest stages of that process. Such research is no longer possible for most Western and Asian populations, as the necessary data were not collected at the time their transitions were getting underway. Here it is possible, via prospective data collection, to observe the social dynamics underlying the process of adoption of modern contraception from the earliest stages of that process. Such research is no longer possible for most Western and Asian populations, as the necessary data were not collected at the time their transitions were getting underway. The ability to derive lessons from Ghana's experience will be greatly enhanced by carrying out research in both southern and northern sites, because of the sharp contrast these two regions present in economic development, social and cultural systems, and stage of demographic transition. In the south, research will be fielded in the Western, Central and Greater Accra regions. In the north, the investigators will utilize the demographic surveillance system that has been established by the Navrongo Health Research Centre in rural kassena-Nankana district and will exploit the large-scale family planning experiment that went into the field in early 1996. Specific objectives include: (1) To test the impact on the adoption of modern contraception of social learning and social influence, including effects on the demand for children and contraceptive costs; (II) To examine how social structure (especially kinship systems), the nature of gender relations, political, economic, and religious organizations, and the accessibility and quality of services; (III) To explore how program efforts and the mass media complement the effects of social learning and social influences; and (IV) To refine methodologies for assessing social effects on the adoption of modern contraception.